Regulation of phospholipase A 2 activity in cockroach ( Periplaneta americana) fat body by hypertrehalosemic hormone: evidence for the participation of protein kinase C

Abstract

Phospholipase A 2 (PLA 2) associated with the membrane fraction of trophocytes from Periplaneta americana fat body increases by as much as 100% when the cells are incubated with hypertrehalosemic hormone (HTH-II). Activation with HTH-II is approximately halved by inclusion of the PKC inhibitor sphingosine in the incubation medium. Because activation of PLA 2 by HTH-II is blocked by the GDP analogue GDP-β-S, and the unactivated enzyme is activated by the GTP analogue GTP-γ-S it is likely that a G protein is involved in activation of the enzyme. Activation of PLA 2 was also achieved by treating the trophocytes with the synthetic diacylglycerol 1-oleoyl-2-acetylglycerol in the presence of thapsigargin. This supports the view that protein kinase C is also involved in the activation process.